Automatic telephone system



June s, 1941. f

e. A. ANDERSON 2.244.596

AUTOMATIC TELEPHONB SYSTEM Filed Dec. 2, 1939 2 Sheets-Sheet 2 N N ByG.A.ANDERSON W @w@a TTOR/VEV Patented June 3, 1941 AUTOMATIG TELEPHONESYSTEM Gustave Adolph Anderson, Albany, N. Y., assignor to AmericanTelephone and Telegraph Company, a corporation f New York ApplicationDecember 2, 1939, Serial N0. 307,332

6 Glaims.

Ths invezntion relates to automatic telephone systems and moreparticularly to systems of the type referred to as community dia1Systems, i. e. small automatic systems for small tovvns and villages.Such Systems are usually unattended but are provided with brunkingfacilities to a distant larger 01fice sometimes called a master. Due,however, 150 the general service requirements of such a systemsimplicity and 10W co-st are very important and therefo-re variousfeatures usually found in large systems have been eliminated in -thesesma11er equipments a-s, for examp1e, facilities for enabling a tolloperator 110 rering a subscriber over a previously establishedconnection, which facilities are in some cases desirable, for exampleWhen a subscriber who makes a 1arge number of toll Balls desires 120have several ca1ls completed o-ne after the other as fast as theoperabor can com-plete them,-

withouo 1:he delay incident t0 building up a counection for every -calland then perhaps, on accasi-on, finding the line busy. Ooviously, 'themost efilcient method. for providing this service would be to hold theconnection between the toll openat or over the trunk to the subscribers1ine and recall the subscriber by ringing on bis line as soon as eachca1l was ready. As previous1y mentioned, arrangements where=by acommunity ofilce sub-scribers line can be he1d and rerung repeatedly atthe will o-f a m11 operator are not or-dinarily furnished in smallsystems of this type fior the reason that the cost o-f 1:he addedequipment cannot in m-ost cases be justified.

An object of the present invention is therefore to provide facilities01' a re1aively simple nature whereby an operator in a distant exchangecan establ=ish and hold a connection t-o a subscribers 1ine, in anexchanse of the type described, and thereafter cause ringing current tobe connected the-reto as often as desired.

Further, it is desirable in Systems cf this nature that a distantoperabor be able, in case an attempt is made either by herse1f or anysubscriber to complete a ca11 to a community oflice subscriber andreceives a 1=ine busy indication, to verify the fact that the 1ine isactually in use by overriding the busy indicabion and estabh'shing aconnection 130 the desired 1ine, either t0 mere1y verify th-e busycondition or vin a more extreme Gase 110 converse with the partiestalking and ask them to make way for an emergency cal1, such as a cafl1for police er 190 report a fire.

Busy test Veri=fication facilities are now provided in 1arge automaticexchanges and the- -srn=aller community exch-anges can be arranged t0provide this service by employing suitable known equipment but theexpense of such faci1ifies frequently cannot be justified for sma1lexchanges -of the type in question.

I1. therefore is a further object of the invention toprovide a simpleand practicable arrangement for small exchanges whereby a busy ca11edline can be seized by certain predetermined cal1- ing lines so establisha talking connection therewith and when the original busy condition isremoved, to fing an said. 1ine.

A feature of the invention whereby bo-th 0f the forgoing objects areattained resides in the emp1=oyment o-f a :special no test connectorswitch so vvi-redand arranged that it may be controlled over certain1ines 01 group of lines as, for examp1e, brunks from an operatorsposition, t-o connect t0 any line available to the switch, regardless ofthe busy condition 0f said line, and When the 1ine is id1e, i. e.receiver 011 h00k, 1:0 ring thereon.

A fur-ther feature resides in auxiliary circuii; means as-sociated Withcertain predetermined subscribers 1ines -available said no testcounector whereby when one '0 f these lines is being he1d by anautomatic switch an a regular sonneotinn and is subsequently seized bythe no test connector, the first connected switch will Joe disconnectedtherefr-om, except for a high impedance -connection which in pracbicemay be a small condenser, during the period the 1ine is engaged by theno test switch. When the 1ine is rung by ehe no test switch on1y anaudible ringing tolle will be transmicted. back through the firstswitch.

'I'he invention will be understood from the following description whenread in connection With the accompanying drawings, Figs. 1 and 2 ofwhich, when placed together With Fig. 1 above Fig. 2, represent aso-called community d=ia1 exchange including calling and -ca11ed localstations and trunks inooming thereto from a dis- 1:ant master office,which exchange is arranged 150 provide the facilities sei; forth in theforegoing objects and features of the invention.

The arrangement whereby the present sequence cal1 service feature isobtained. Will now be described.

Referr ing the dnawings, X, A and. B are loca1 stati-ons 0f thecommunity dfi-a1 exchange and OOI and 002 are oord circuits arranged fordialing and located in a distant master office which cord -circuits haveaccess to the communitsr rotadzes the wipers cf ehe connec-tor 110 thede-.

sired. 1ine, which connector appears in the banks 0f 2.11 the selectorsS, S! anti S2. Ab this point it may be mentioned that the seiector S,serving local subscribers such as X, has a vacant Level, for ex-amplethe upper or top Level aus shown in the drawings, in which 1evel ncconnector trunks are terminated.

N'IC represents a special or no test connectol also arranged for thesame type of ringing 001'1- trol as the regular connector C but modified120 the extent that it is unresponsive to a busy coudition encounteredon the test terminal 016 a dialed subscfibers line andtherefore itswipers stap -on the terminais of any line to Which they are advancedirrespective cf ehe busy or id1e condition thereof.

It Will be noted that the connector C appears in the banks cf a.11 theselectors S, SH, and. S2, but the connector N'IC on1y appears in thebanks of selec:tors S! anti S2, i. e., the selectors termina.ting thetrunks TK! and TKZ from the master ofiice, and more specificaily appearin the upper or top 1evsl of these selectors which level, as beforemenoibned, is vaczmt in selector S and therefore it will be obvious thatwhereas an operator at the master oce 02m by means cf a cord circuitam). one cf the trunks TKI or TK2 reach a desired subscribers 1ine A B,etc. by way of either the regular ccnnector C 01' the special notestconnector NTC a local subscriber such as station X can =only obain aconnection With these lineg by way 0f the regular connector C, that isto say, a, loca1 subscriber can only reach anoi-her local subscribersline if that line is id1e, whereas an operator at the master ofi1ce canobtain a connection With a loca1 subscribers line either by way 0f theregular -connector C, if the desired 1ine is id1e 01 via the specialno-test counector NTC regardless of whether the line is idle er busy.

Meang whereby a subscriber such as X obtains connection With anothersubscriber such as A o1 B, which involves standard line finders,selectors and connectcrs forma 110 =part cf the present invention and nodetailed description thereo:f is necessary it being sufiicient tomention that when the caliing subscriber removes bis receiver from thehook a line finder LF seizes the line und extends it to an isi1eselector such as S following which the subscriber a=ctuates bis dial sotransmit the code digits of the desired line foilowed Joy the digitdesignating th e ende ring cf the wanted party1ine subscriber, whichdial Impulses successive1y control the movement of the wipers of theselector S, connector C and the Code switch which forms a, part of theconnector.

Let us assume, however, that the subscriber B is a. very large user ofiong disbauce toll facilities anti frequently desires t0 communica.te inrapid succession With a number of distant stations. As Will beunderstood, the ordinary rcutine in handling such ca]ls is for thesubscri-ber to dial the teil operator with whom he is connected by means0f the usual facilities (not shown) and When the operacoranswers to giveher the necessary details of the desired connections after Which, unlessthe calls can be completed while the subscriber remains a1; bistelephone, he Will be told replace bis reoeiver on the hook anal that heWill be called as soon as the desired connections can be meide. When theoperator is ready With the first call, she will connect one 0f her cordcircuits, for example OCI, With a trunk, for example 'IKI, anal diai theregular ende digits 0f ehe ca11ing subscribers 1ine which, for examp1e,may be 2i2 as indicated by the drawings. 'Ihe first digit dialed Willraise the wipers of the sel'ector S to the proper leve1, for example thesecond leve1 as shown, und ab the conclusion of the pulses the selectorwill rotate its Wipers into contaci; with the first sei: 0f terminalswhere they will remain if we assume t'ne connector C 170 -be idle. 'Iheoperator is ncw connected to :conn'ector C anal the next two digitsdia1ed Will raise und.

rctate the wipers of the connector inco engagement With the bankterminals corresponding 170 the line of station B which as shown is thesecond sei: in the first leve1. The operator then dia.1s the final orcode-n'nging digit cf station B and when the subscriber answers ringingwill be tripped.

When the subscriber restores his receiver 110 the switchhook at the end01" the conversation, thesupervisory 1amp before the toll operator willbe lighted. However, as other calls are 110 be completed in sequence thesame subscriber, the operator Will not disconnect from the trunk at thistime, but Will immediately;proceed With the next cal1.

When the cperator is ready With the nexi; aal], as the regular connectorC is still in the talking condition, a.nd the ringing equipment 1 nowlocked out, she is unab1e 110 recall the subseriber over the originalconnection, i. e. cord OCI, trunk TKI, selectorl -and connector C but bymeans cf special connector NTC and the special equipment associated Withthe 1ine of subscriber B, comprising the present invention, she is a:b1e130 accomplish this function in the following manner.

In order t0 ring the subscriber B under the above -condition theoperator Will connect a second cord OC2, -for exampie, With anothertrunk 'I'K2 130 the community o1fice, and first dia1 the 1evel of thetrunk selectors reserved for the special connector N'I'C Which from thedrawings is shown as the upper or top level cf selectors S! arm S2. Asselector S2 is associatecl With trunk TK2, and if We assume the selectcrto have ten Levels, the operator Will dia1 (l, i. e., transmit tenpulses by means of her dial, followed by the digit pulses i anal 2necessary 110 advance the special connector into engagement With'thesubscribers Iine terminals which as before am the sec0nd in the firstievel. In this connection, as before mentioned, special connector NTCl's on1y multipled in selector 1evels accessible to the master officetrunk Which in the present case is the upper o1 tenth level of selectorsS! and S2 and therefore it Will Joe evident that local subscri'bers ofthe community office as, for exampl-e, station X are unabie to gainaccess to this connector, the reason for which is obvious.

When the selector S2 raises its wiperg the tenth level and rotates theminto contact with the fi1st Set; cf terminals, battery through the 1owerwinding cf the so-cailed C relay 2 in the connector NTC and over the Clead 3 causes the selector 150 extend the tip and ring of the trunkthrough to battery and ground in series withthe upper and lower windingsof the line relay I. Relays 2 and I operate, followed immediately by theso-called B relay 4. Relay 2 in operating closes its contacts therebypreparing the impulsing circuit of the vertical magnet VERT. Relay 4, atits contacts 1, grounds the C lead 3. The connector NTC with relays I, 2and 4 operated is now in readiness 130 receive Ehe second and thirddigit impulses -from Ehe operators cord at the master olfice. As theline cf subscriber B terminates on the second terminals of I:he firstleve1 the wipers 8, 9 and III must be ralsed one step thereby requiringa single relea.se and subsequent reoperation -of relay I. Therefore,when relay I releases, the =pulsing circuit is closed to the verticalmagnet in parallel With the upper winding of relay 2 and the wipers areraised to the first level, the vertical ofI-normal contaots I2 areopened thereby opening the starting circuit through the lower winding ofrelay 2 and the contacts I3 are closed thcreby preparing a circuit 60operate the release magnet I4. When relay I reoperates, relay 2rel-eases and transfers the pulsing circuit from the vertical magnet 1:0relay I I in parallel with the rotary magnet ROT.

When the operator transmits the next o1 third series of impulses, two inthis case, relay I releases and reoperates twice. On alle first releaseo! relay I, relay II operates in parallel With the rotary magnet ROT inthe following circuit: Ground, back contact of relay I,contacts I5 cfrelay 4, back contacts 0f relay 2, and from this point one brauchextends through the winding of relay II to battery and the other brauchcan be further traced over contacts I6 of relay I1, contacts I8 of relayI9, conductor 20, contacts 2I of relay 22 and Winding cf rotary magnetROT, also 120 battery. Relay I I in operating closes the followingcircuit so opera.te relay 23: Ground, contacts 24 0f relay 4, contacts26 of relay 22, contacts 21 of relay II, contacts 28 of relay I1 andc0nductor 34 120 battery through the upper winding of relay 23. Relay 23operates and locks over its contacts 30 in series with the lower windingof relay I1 to ground at. contacts 24 cf relay 4 in the followlngcircuit: Ground, contacts 24 of relay 4, concluctors 25 and 3I, contacts30 of relay 23, contactg 32 cf relay 33, contact 34 of relay 22, lowerwinding cf relay I1, conductor 34 and upper Windlng cf relay 23 110battery. Relay 23 ab its contacts 35 also connecIs-s ios lower windingin parallel with the upper Winding of relay I1. Relay I1 does notoperate at this time, however, as its lower winding is short circuitedat contacts 21 0f relay II.

In response to the transmission of owo dial pulses the rotary magnet ROTmoves the wipers 8, 9 and I0 two steps into contact with the secondterminal cf the first level of the connector switch during whichinterval relayg 4 and I I re main opera'bed.

When relay I reoperates foll0wing the sec0nd impulse, relay II after ashort interval releases thereby opening its contact 21 and removing theshort circuit from the lower winding of relay I1 which relay thereuponoperates in the followlng circuit: Ground, contacts 24 of relay 4,conduct0rs 25 and 3I, contacts 30 of relay 23, contacts 32 of relay 33,contacts 34 of relay 22, lower wlnding of relay I1 and the upper windingcf relay 23 120 battery.

Relay I1 in operating opens its contacts I6 thereby interruptlng theclrcult of rotary magnet ROT and closes its contacts 36 therebyextending the impulse circuit to the rotary magnet 31 of the minor crringing code selector switch and ab its contacts 38 completes anenergizing circuit for relay 39 which can be traced from grond, contacts24 of relay 4, contacts 26 of relay 22, conductor 40, contacts 38 0frelay I1 and winding of relay 39 to battery. Relay 39 operates in turnoperating relay I9 over ii;s cantacts 41 to ground at contacts 24 ofrelay4. Relay I 9 locks so ground at c0ntacts 24 of relay 4 over itscontacts 4I and ab its contacts I8 introduces another break in theprevious circuit for the rotary magnet ROT. Relay I9 also closes itscontacts 42 thereby operating relay 43, the circuit for which can betraced from ground at contacts 24 0f relay 4, contacts 26 cf relay 22,conductor 40, contacts 42 of relay I9 and winding of relay 43 1:0battery. Further, relay I9 closeg its contacts 44 and 45 therebyshunting the normally opened contacts 46 and 41 of relay 33 by fing-backcondensers 48 and. 49, respectively.

Relay 43 in operating closes a listening circuit between i;he tip =andring cf the line and the wiper 6 and 9 including condensers 50 and 5I.'I'he connector is now in the verification position, the operator at themaster 0ffice is connected 1:0 the called subscribers llne and is able.to determine if ehe line is in use by li-stening for conversation.

If the line is idle the operator ca.n ring the subscriber5 station B bydialing the final or code digit which Operation 1Sas follows: Relay Ifol- 10Ws the impulses of the last series dialed by the operator andwhen 113 releases for I;he first impulse, lt recloses the circuit forrelay II which reoperates in parallel with the rotary magnet 31 of thecode switch. Relay II in operating opens its upper contacts therebyopening the listening circuit previously mentloned and closes itscontacts 21 thereby connecting ground to the upper winding of relay I1and the lower winding of relay 23. Relay 23 releases at this time due tothe fact that the flux generated in the lower winding opposes andneutralizes the flux in the upper Winzling.

When relay 23 releases, it opens the previously mentioned circuitthrough its lower winding ab its contactg 35 and opens the circuitthrough its upper winding and the lower windlng of relay I1 a.t itscontacts 30. Relay I1 holds operated, during the pulses, over itscontacts 55, contacts 21 of relay II, contacts 26 of relay 22 andcontacts 24 of relay 4 to ground.

The code switch MS is moved forward under control cf the rotary magnetand on the fi.rst step actuates the elf-normal switch 56 to close itscontactg thereby preparing circuits to operate the release magnet 51 andrelay 22.

Relayg 4 and II remain operated during the pulsing.

AI; the and of the last impulse, relay I I releases and recloses at itsupper contacts the listening circuit previously referred to. Relay IIalso opens its contacts 21 thereby deenergizing the upper winding ofrelay I1 which thereupon releases open at its contacts 38 the circuitfor relay 39 which releases. Relay I1 also opens its contacts 36 todisconnect the rotary magnet 31 and, by closing its contacts 53,connects the lower Winding of relay 22 to the third wiper I0 of theconnector switch. When relay 39 releases lt opens, at its contacts 4I,the operating circuit for relay I9, but relay I9 remains operatedthrough its contacts 4I to ground a1: contacts Relay39 in releasing alsocloses its lowermost back contacts thereby connecting ground a.t 0011-tacts 24 of relay 4 through the lower winding of' relay 22 t.o the wiperI0. The test; terminal of the line of subscriber B, which line isspecial, is noi: multipled to the corresponding terminal in the bank ofconnector C and therefore it is always at battery potential and relay 22Will operate Which locks through its upper Winding and contacts 57 andcontacts 58 of re1ay 4 t ground. Rela5 22 in closing its contacts 54nonnects direct ground over conductor 52 m the wiper I5. Further, relay22 closes its contacts 59 thereby connecting ground over contacts 60 ofrelay 33 to the ringing machine starb Iead S! which extends to theringing machine, not shown. Relay 22 further connects relay 62 across:the tip am! ring of the line, opens ab contacts 26 the ground connection.for relay 43 anti ab contacts 63 and 65 connect.s the upper winding ofrelay 23 to the soca.l1ed pick-up ]ead 66 from the ringing machine whichcan be traced from battery, upper winding of re1ay 23, contacts 63 ofrela.y 22, contacts 32 of rela.y 33, contacts 64 of relay 23 andcontacts 65 of re1ay 22 to the pick-up lead 55 which will be grounded abthe ringing machine at the proper point in the ringing cyc1e. Relay 43releases and reopens the listening circuit. It Will be noted at thistime that the line of subscriber B is specia.l in that an auxilia.ryline circuit is connected between the subscriber and the regularsubscribers line circuit which auxiliary circuit comprises a relay andsma1l capacity condensers 68 and 69 for the purpose of providing thespecia1 sequence call feature which is a characteristic cf the presentinvention and therefore when relay 39 re1eases a.nd closes its lowermostback contacts 120 complete a. circuit from ground thr0ugh the lowerwinding of relay 22, 130 the conductor 52 anal. the third wiper of theconneetor relay 61 operates thereby introducing condensers 68 and 69 inthe connection between the 1ine of subscriber B and the bank terminalsof regular connector C which terminals vve have assumed a.re engaged bythe wipers o1 that connector and he1d in fuhat position from the masteroffice. V

'Ihe capa.city of condensers 63 and 59 is very small (of the oraler of.04 microfarad 0r sma.ller, depending on the characteristic of t.heringing current employed) and therefore they introduce ahigh impedancebetween the tip and ring bank terminals 0f the two connectors throughWhich when ringing current is a.pplied to the 1ine of subscriner B byconnector NTC only a small portion will be transmitted back to themaster oifice through connector C which sma11 current is on1y suflicientto serve a.s an indication to the operator that the cal'led subscriber Bis being rung.

When the ringing equipment (not shown) Starts a new cycle of code rings,the pick-up lead 66 is grounded in a well-known manner therebyreoperating relay 23 in a circuit which can be traced from ground on thepick-up lead 66, sontacts 55 of relay 22, contact 54 cf re1ay 23,Contacts 32 of relay 33, contacts 63 of relay 22, :and upper winding ofrelay 23 of battery. Relay 23 thereupon locks over its contacts 30 toground at eontacts 24 of relay 4 and closes its contacts 70 and Hthereby connecting the segments 12 and 13 of the switch MS 130 the ringam]. tip wipers 8 anti 9. Depending on the position of the switch MS theselected ringing code will be transmitted 130 the called 1ine in serieswioh the upper winding of relay 33 which relay will operate when thecalled subscriber answers. If the last digit dialed is between 1 and 5,the top wiper 14 of switch MS will connect the selected generator lead170 the top 01 ring wiper 8 and the tip wiper 9 will be connectedthrough the lower Wiper 19-0f switch MS and the upper winding of 1e1ay33 to battery. If the digit dialed is between 6 and G, the aboveconnection Will be reversed with respect t-0 the wipers.

As before mentioned, a small portion of this ringing current Will flowthrough t.he condensers 68 and 69 and the connector C to the trunk 'IKlanal thence 130 the operator ab the master ofifice as an audible ringingtone.

When the ca11ed subscriber B answers by removing bis receiver from theswitchhook, the rela.y 33 operates in series With the subscribers set inthe following circuit: ground on the selected generator 1eaol, segment72 and Wiper 'a'4, of the switch MS, resistance lamp 75, contacts HI 0frelay 23, conta.cts 76 of relay 33, ring comductor of the connector,wiper 8 and the se lected ba.nk terminals, over the subscribers Iine,through the subscribers set and back to the connector anal wiper 9,'c0ntacts T. cf relay 33, contacts H 015 relay 23, resistanc e lamp I8,wiper 19 and segment 73 of the switch MS, conductor 84 and upperWinzling of relay 33 to battery. Rela.y 33 operates and. locks over itslower winding to ground at contacts 580f relay 4. Relay 33 also opensits contacts 76 and 17 thereby disconnecting ringing through the codeswitch MS, by opening its contacts 32, relea.ses relay 23, and at itscontacts 46 and 41 closes the 1ine through, and by opening its contacts60 removes ground from the ringing machine.start lead 6I.

Relay 62 which is bridged across the tip and ring conductors operatesand reverses battery and ground back through the selector S2 and trunkTK2 to the operator thereby extinguishing the cord supervisory lamp (notshown) .as an indication that the subscriber has answered. At this timethe vertical oif-normal contacts I2 are open and contacts 13 are closed,the contacts of the code switch ofl-normal springs 56 are c1osed andrelays l, 4, 33, I9, 62 and22 a.re operated.

When the operator notes from her supervisory la.mp on cord OC2, that thesubscriber B has answered, she discomiects the cord from the trunk TK2whereupon -ohe circuit of relay l is opened which re1ay thereuponreleases thereby releasing re1ay 4 which in releasing removes ground abits contact5 24 from the c0nductor 52 Which is connected to the thirdwiper I0 of the connector thereby releasing re1ay 61 in the subscribersline and removing the high impedance condensers 68 and 69 between this1ine and the bank terminals of connector C. The release of re1ay 4 alsoinitiates the release of connector NTC which restores 1:0 normal inreadiness f 0r another ca1l. Conversation now proceeds in the usua1manner ab the end of which, if there are still other calls to becompleted, thesubscriber Will restore his receiver but the Operator willnot disconnect her cord circuit OCI from the trunk 'IKl thereby stillholding the subscribers line in readiness for completion of the nextcall.

When the operator is ready to establish the next connection, she Willagain connect the cord OC2 to the trunk 'I'K2 and transrnit dig*it im-'pulses as befo-re to seize anal ring on the subscribers 1ine. 'I'hisprocess will be repeated as long as the operator has ca1ls to becompleted. When the series of calls are completed, the operator willdisconnect from trunk TKI whereupon connecdsor C releases in the usualmanner and the subscribers 1ine is free for other ca1ls.

If connector N'IC is used merely to verify the busy or idle condition ofa regular subscribers 1ine, such as the line at subscriber A, forexample, ground will not be connected to couductor 52 and wiper I and.the 1ine will not be made busy 130 other connectors, unless a1- readybusy 01' the final digit is dialed. In this case, however, the operatorwill not (in most cases) dial the final or code ringing digit and afterverification will immediately re1ease the special conneetor.

In case it is desired to make connector NTC inaccessible to theselectors such as S! and S2, busy key 8I can be operated, therebyremoving battery from conductor 3 leading back frem re- 1ay 2 so theselector.

What is claimed ist 1. In an automatic telephone exchange, a subscribersline, a first connector switch having access thereto, ancl for makingsaid line busy when connected thereto, a no test connector having accessto and adapted 120 seize said line regardless of its busy condition,means in said no test connector for applying ringing current to said1ine, and meang in said. line responsive t seizure by said no testconnector to connect a high impedance between the line and t'he firstconnector, 120 exclude from the first calling line all but a smallamount of the ringing current appliecl to the ca1led 1ine by the no-testconnector.

2. In an automatic telephone exchange, a subscribers 1ine, a firstconnector switch having access thereto, and for making said line busywhen connected l;herozzto a 110 test connector having access t0 andadapted to seize said line regardless of its busy condition, means insaid no test connector for applying ringing current 130 said line, andmeans in said 1ine responsive toseizure by said no test connector toconnect a sma1l capacity condenser between the 1ine and. the firs1;connector.

3. In an automatic telephone exchange, a subscribers line, a firstconnector adapted to seize said line only if id1e, and to thereaftermake said line busy, a second connector adapted 1:0 seize said 1ineregardless of its busy or idle condition, means for transmittingimpu1ses to move said second connector into connection with said line,means in said second connector responsive to the transmission thereto ofa predetermined number of impulses after said line has been seized soapply ringing current to said line, and meang associated with said 1ineresponsive 170 its seizure by said second connector to interpose acondenser betvveen said 1ine and said first connector.

4. In an automatic telephone system, a subscribers 1ine, a firstconnector am]. a test counector, each having access 130 said line saidtest connector being adapted seize said line regardless of its priorseizure by said first connector, means in said test connector responsiveto dia1 pulses transmitted thereto subsequent to its seizure of said1ine 170 cause ringing current to be connected to the line, and meansassociated with the 1ine responsive to its seizure by said testconnector introduce a relatively high impedance between said firstconnector and ehe 1ine.

5. In an automatic telephone system, first and second connecoors, atelephone 1ine terminating in contact of both connectors said firstconnector being arranged seize said 1ine only when idle and said secondconnector being arranged to seize said 1ine regardless 015 its busy orid1e condition, am! means in said line responsive 120 seizure 'thereofby said second connector to interpose a high impedance between said 1ineand the coutacts of 1;he first connector on which said line terminates.

6. In an automatic telephone exchange, a first calling line, a cal1ed1ine, a firsr, connector switch having access to said called 1ine andcontrolled over said first calling 1ine, said first connector switchbeing adapted 120 make said. callecl 1ine busy when connected there*to,a second ca1ling 1ine, a no-test connector controlled over said secondcalling line and having access to and adapted to seize said called. lineregardless cf its busy condition, means in said no-test connectorcontrolled over said second calling line for applying ringing current tosaid. called. line, and means in said called line responsive to seizureof the line by the no-tesd; connector 130 introduce a high impedance inthe connection between said first 001'1- nector and the called line toexclude from the first calling line all but a. small amount 01 theringing current app1ied to the called 1ine by the no-test connector.

USTAVE A. AI TIDER SONv

